gnome-shell: Remove unwanted margin from some buttons

Fixes 1px gap between some buttons, that was inherited from the
default theme after GNOME Shell 42 update.

Author: jnsh

common/gnome-shell/42/sass/_common.scss

@@ -261,6 +261,7 @@ StScrollBar {
 
   &-linked-button {
     height: if($variant=='light', 39px, 38px);
+    margin: 0;
     padding: 0;
     box-shadow: inset 0 0 black;
     border-top-width: if($variant=='light', 0px, 1px);
@@ -2179,6 +2180,7 @@ $_dash_bottom_margin: 20px;
     spacing: 3px;
   }
   .notification-button {
+    marging: 0;
     padding: 4px 4px 5px;
     min-height: 0;
     font-weight: normal !important;
@@ -2233,6 +2235,7 @@ $_dash_bottom_margin: 20px;
 }
 
 .hotplug-notification-item {
+  margin: 0;
   padding: 2px 10px;
   font-weight: normal !important;
   @extend %button;